Sliding windows of the above type are increasing in popularity as their advantages over more conventional swinging windows become apparent. Due to the inherent balance of sliding windows, when they are moved to an open position they remain there, whereas swinging windows need some sort of locating means to maintain the open position. Furthermore, if swinging windows are arranged to open inwardly, the window sills have to be kept clear of objects, such as plants, so that movement of the window is not hindered.
The main disadvantage with sliding windows is the problem of obtaining a satisfactory seal against, particularly, wind and rain. With swinging windows, the problem is not as acute because, when closing windows of this type, the window is pushed against its surrounding frame before being locked in the closed position. Thus, good sealing can be achieved by either ensuring a close fit between the window and frame or by providing a thin layer of insulating material around the frame, or of course, by both measures. With sliding windows, conversely, there is no relative movement of the sashes towards each other and so up until now satisfactory sealing has required high precision in manufacturing and installing such windows so that the sliding elements lie as close to each other as possible.
A further typical disadvantage, particularly with sliding doors, is that several catches or handles have to be operated in order to be able to slide open the doors.